U.S. patent application number 12/353692 was filed with the patent office on 2009-05-14 for knee system and method of making same.
This patent application is currently assigned to ZIMMER, INC.. Invention is credited to Oludele O. Popoola, Joel G. Scrafton.
Application Number | 20090125115 12/353692 |
Document ID | / |
Family ID | 40624503 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090125115 |
Kind Code |
A1 |
Popoola; Oludele O. ; et
al. |
May 14, 2009 |
KNEE SYSTEM AND METHOD OF MAKING SAME
Abstract
A femoral prosthesis may be formed as a femoral component
incorporating a base material and an articulating material. In one
exemplary embodiment, the base material is a metal and the
articulating material is a polymer. Specifically, the base material
provides strength and rigidity to the femoral component, while the
articulating material contacts a tibial prosthesis or natural tibia
during joint articulation. In one exemplary embodiment, the
articulating material forms the articulating surface of one or more
condyle portions of the femoral component.
Inventors: |
Popoola; Oludele O.;
(Granger, IN) ; Scrafton; Joel G.; (Leesburg,
IN) |
Correspondence
Address: |
ZIMMER TECHNOLOGY - BAKER & DANIELS
111 EAST WAYNE STREET, SUITE 800
FORT WAYNE
IN
46802
US
|
Assignee: |
ZIMMER, INC.
Warsaw
IN
|
Family ID: |
40624503 |
Appl. No.: |
12/353692 |
Filed: |
January 14, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11749598 |
May 16, 2007 |
|
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12353692 |
|
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61020900 |
Jan 14, 2008 |
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Current U.S.
Class: |
623/20.14 ;
623/20.31 |
Current CPC
Class: |
A61F 2310/0058 20130101;
A61F 2/3859 20130101; A61F 2002/30937 20130101; A61F 2/389
20130101; A61F 2250/0018 20130101; A61F 2310/00023 20130101; A61F
2310/00886 20130101; A61F 2310/00317 20130101; A61F 2310/00029
20130101; A61F 2/38 20130101; A61F 2310/0088 20130101; A61F
2002/30014 20130101; A61F 2002/30934 20130101; A61F 2310/00239
20130101; A61F 2310/00131 20130101; A61F 2310/00017 20130101; A61F
2310/00281 20130101; A61F 2/3094 20130101; A61F 2310/00203
20130101 |
Class at
Publication: |
623/20.14 ;
623/20.31 |
International
Class: |
A61F 2/38 20060101
A61F002/38 |
Claims
1. A knee prosthesis, comprising: a femoral component formed from a
non-polymeric base material and a polymer articulating material,
said femoral component having at least one condyle portion formed
from said non-polymeric base material, said at least one condyle
portion having an upper surface and a wall at least partially
defining a groove, said polymer articulating material received
within said groove, said wall of said at least one condyle portion
surrounding said polymer articulating material, said polymer
articulating material defining an articulation surface configured
for articulation against one of a proximal tibial prosthesis and a
natural proximal tibia, said articulation surface of said polymer
articulating material positioned substantially flush with said
upper surface of said at least one condyle portion.
2. The knee prosthesis of claim 1, wherein said non-polymeric base
material comprises a metal.
3. The knee prosthesis of claim 2, wherein said non-polymeric base
material is selected from the group consisting of titanium, a
titanium alloy, cobalt chromium, cobalt chromium molybdenum,
stainless steel, and porous tantalum.
4. The knee prosthesis of claim 1, wherein said non-polymeric base
material comprises a ceramic.
5. The knee prosthesis of claim 4, wherein said non-polymeric base
material is selected from the group consisting of alumina,
zirconia, silicon nitride, and silicon carbide.
6. The knee prosthesis of claim 1, wherein said polymer
articulating material is selected from the group consisting of poly
ether ether ketone, fiber reinforced poly ether ether ketone, ultra
high molecular weight polyethylene, cross-linked ultra high
molecular weight polyethylene, polycarbonate urethane,
polyphenylene, and polyether ketone ether ether ketone.
7. The knee prosthesis of claim 1, wherein said at least one
condyle portion further includes a lip, said lip cooperating with
said wall to define said groove, said lip surrounding said polymer
articulating material, wherein said lip facilitates retention of
said polymer articulating material within said groove.
8. The knee prosthesis of claim 7, wherein said lip extends into
said groove, said lip and said wall of said at least one condyle
portion defining an obtuse angle.
9. The knee prosthesis of claim 1, wherein said articulating
material is positioned in said groove by one of thermal spraying,
dynamic cold spraying, insert molding, compression molding,
injection molding, laser cladding, and press fitting.
10. A tibial prosthesis, comprising: a tibial component having a
polymeric body and at least one non-polymeric articulating portion,
said polymeric body having an upper surface, said at least one
non-polymeric articulating portion having a perimeter and an
articulating surface configured for articulating with one of a
femoral prosthesis and a natural femur, said non-polymeric
articulating portion received within said polymeric body, wherein
said polymeric body surrounds said perimeter of said non-polymeric
articulating portion and said articulating surface of said
non-polymeric articulating portion is substantially flush with said
upper surface of said polymeric body.
11. The tibial prosthesis of claim 10, wherein said polymeric body
is formed from a polymer selected from the group consisting of poly
ether ether ketone, fiber reinforced poly ether ether ketone, ultra
high molecular weight polyethylene, cross-linked ultra high
molecular weight polyethylene, polycarbonate urethane,
polyphenylene, and poly ether ketone ether ether ketone.
12. The tibial prosthesis of claim 10, wherein said non-polymeric
articulating portion comprises a metal.
13. The tibia prosthesis of claim 12, wherein said metal is
selected from the group consisting of titanium, a titanium alloy,
cobalt chromium, cobalt chromium molybdenum, stainless steel, and
porous tantalum.
14. The tibial prosthesis of claim 10, wherein said non-polymeric
articulating portion comprises a ceramic.
15. The tibial prosthesis of claim 14, wherein said ceramic is
selected from the group consisting of alumina, zirconia, silicon
nitride, and silicon carbide.
16. The implant system of claim 10, wherein said articulating
surface further comprises a plurality of depressions, wherein said
plurality of depressions facilitate the retention of fluid on said
articulating surface.
17. The implant system of claim 10, further comprising a tibial
tray component, said tibial tray component having a plate and a
stem, said polymeric body of said tibial component configured for
securement to said plate of said tibial tray component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under Title 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Patent Application Ser. No.
61/020,900, entitled A KNEE SYSTEM AND METHOD OF MAKING SAME, filed
on Jan. 14, 2008, and under Title 35 U.S.C. .sctn. 120 of U.S.
patent application Ser. No. 11/749,598, entitled IMPLANT ARTICULAR
SURFACE WEAR REDUCTION SYSTEM, filed May 16, 2007, the entire
disclosures of which are expressly incorporated by reference
herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to knee prostheses and,
particularly, to femoral and tibial prostheses.
[0004] 2. Description of the Related Art
[0005] Prostheses are commonly utilized to repair and/or replace
damaged bone and tissue in the human body. For example, a knee
prosthesis may be implanted to replace damaged or destroyed bone in
the tibia and/or femur and to recreate the natural, anatomical
articulation of the knee joint. In a femoral prosthesis, the
prosthesis may be shaped to replicate one or both of the natural
femoral condyles. A femoral prosthesis may be formed entirely of a
rigid metal, which can be formed in complicated geometries and
withstand the unique load patterns experienced by the femoral
component. After resecting the distal end of the femur, one side of
the femoral component is secured to the bone stock of the femur and
the opposing side of the femoral component is configured for
articulation against a prosthetic tibial component or the natural
tibia.
[0006] A prosthetic tibial component may include a first,
articulating component having a concave condyle portion configured
for articulation against the femoral component. The articulating
component of the tibial prosthesis may be secured to a tray
component that has an opposing side for securing the tibial
prosthesis to the bone stock of a resected proximal tibia. The
articulating component of the tibial prosthesis may be made from a
polymer to facilitate articulation with the femoral component,
while the tray component of the tibial prosthesis may be made from
a metal to provide additional strength and rigidity to the tibial
prosthesis. In this manner, the femoral component and tibial
component work together to replicate the natural, anatomical
articulation of the knee joint.
SUMMARY
[0007] The present invention relates to knee prostheses and,
particularly, to femoral and tibial prostheses. In one exemplary
embodiment, a femoral prosthesis is formed as a femoral component
incorporating a base material and an articulating material. In one
exemplary embodiment, the base material is a metal and the
articulating material is a polymer. The base material provides
strength and rigidity to the femoral component, while the
articulating material contacts a tibial prosthesis or natural tibia
during joint articulation. In one exemplary embodiment, the
articulating material forms the articulating surface of one or more
condyle portions of the femoral component. Additionally, by
utilizing a base material, such as a metal, that is sufficiently
rigid, the base material provides support and rigidity to the
articulating material. In one exemplary embodiment, the base
material surrounds the articulating material to provide additional
support and rigidity to the sides of the articulating material. By
utilizing a femoral component having a rigid base material that
substantially surrounds a more resilient articulating material
defining an articulating surface, stress at the edges of the
articular surface that are generated during knee articulation are
absorbed by the base material. As a result, delamination of, i.e.,
the peeling off of, the articulating material is substantially
prevented.
[0008] In another exemplary embodiment, a tibial prosthesis is
provided in the form of a tibial component including an
articulating surface and an attachment surface. The attachment
surface of the tibial component is configured for attachment to the
resected proximal end of a tibia and the articulating surface is
configured for articulating against the condyle portion of a
femoral component and/or of the natural femur. In one exemplary
embodiment, the articulating surface and the attachment surface of
the tibial component are formed from a single material. For
example, the entire tibial component may be formed from a metal or
a ceramic.
[0009] By forming the tibial component from a single material, the
strength and rigidity of the tibial component is maintained
throughout its entirety. Additionally, any potential backside wear
of the tibial component, i.e., wear between an articulating
component and a tray component, is eliminated. In another exemplary
embodiment, the tibial component may be formed from a plurality of
materials. In this embodiment, the articulating surface may be
formed from a metal and/or ceramic, while the attachment surface of
the tibial component may be formed from a polymer. In one exemplary
embodiment, the attachment surface may be secured directly to the
resected proximal tibia. Alternatively, in another exemplary
embodiment, the tibial component may be seated upon a tibial tray
component that provides additional rigidity to the tibial component
and cooperates with the tibial component to form the tibial
prosthesis. Additionally, by providing a polymer layer between the
resected proximal tibial or the tray component and the articulating
surface, a cushioning effect may be provided within the knee
prosthesis, which may provide a better fit and feel to the
patient.
[0010] Advantageously, by forming the articulating surface of the
femoral component from a polymer and forming the articulating
surface of the tibial component from a metal and/or a ceramic, the
wear of a prosthetic knee incorporating the femoral and tibial
prostheses of the present invention is substantially reduced. For
example, preliminary testing has indicated that the present design
results in a reduction in wear of up to 35% over traditional knee
prosthesis designs in which the femoral component is metal or
ceramic and the articulating surface of the tibial component is a
polymer.
[0011] In one form thereof, the present invention provides a knee
prosthesis, including: a femoral component formed from a
non-polymeric base material and a polymer articulating material,
the femoral component having at least one condyle portion formed
from the non-polymeric base material, the at least one condyle
portion having an upper surface and a wall at least partially
defining a groove, the polymer articulating material received
within the groove, the wall of the at least one condyle portion
surrounding the polymer articulating material, the polymer
articulating material defining an articulation surface configured
for articulation against one of a tibial prosthesis and a resected
proximal tibia, the articulation surface of the polymer
articulating material positioned substantially flush with the upper
surface of the at least one condyle portion.
[0012] In another form thereof, the present invention provides a
tibial prosthesis, including: a tibial component having a polymeric
body and at least one non-polymeric articulating portion, the
polymeric body having an upper surface, the at least one
non-polymeric articulating portion having a perimeter and an
articulating surface configured for articulating with one of a
femoral prosthesis and a natural femur, the non-polymeric
articulating portion received within the polymeric body, wherein
the polymeric body surrounds the perimeter of the non-polymeric
articulating portion and the articulating surface of the
non-polymeric articulating portion is substantially flush with the
upper surface of the polymeric body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following descriptions of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0014] FIG. 1 is a perspective view of an exemplary embodiment of a
femoral component of the present invention;
[0015] FIG. 2 is another perspective view of the femoral component
of FIG. 1;
[0016] FIG. 3 is a perspective view of the femoral component of
FIG. 1 depicting the femoral component prior to the attachment of
articulating material;
[0017] FIG. 4 is another perspective view of the femoral component
of FIG. 3;
[0018] FIG. 5 is a perspective view of an exemplary embodiment of a
tibial component of the present invention;
[0019] FIG. 6 is a plan view of another exemplary embodiment of a
tibial component of the present invention;
[0020] FIG. 7 is a cross-sectional view of the femoral component of
FIG. 1 taken along line 7-7 of FIG. 1;
[0021] FIG. 8 is a cross-sectional view of another exemplary
embodiment of a femoral component of the present invention taken at
the same position as the cross-sectional view of FIG. 7;
[0022] FIG. 9 is an enlarged view of the portion of the femoral
component of FIG. 8 encircled in dashed lines;
[0023] FIG. 10 is a cross-sectional view of another exemplary
embodiment of a tibial component of the present invention taken at
the same position as the cross-sectional view of FIG. 4;
[0024] FIG. 11 is a cross-sectional view of the tibial component of
FIG. 6, taken along line 11-11 of FIG. 6;
[0025] FIG. 12 is an exploded, perspective view of a tibial
prosthesis including the tibial component of FIG. 6 and a tibial
tray component; and
[0026] FIG. 13 is a cross-sectional view of the tibial prosthesis
of FIG. 12 taken along line 13-13 of FIG. 12.
[0027] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate exemplary embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0028] Referring to FIGS. 1-4, a femoral prosthesis is shown in the
form of femoral component 10, which is formed from base material 12
and articulating material 14. Femoral component 10 includes condyle
portions 16, 18 that define upper surfaces 19 and are formed from
base material 12. As used herein the phrase "condyle portion" is
defined as a section of material that has a geometry substantially
replicating or mimicking the anatomical geometry of a natural
femoral condyle. While several features of femoral prosthesis 10
are described and depicted herein with specific reference to
condyle portion 18, condyle portion 16 may be formed in a
substantially similar manner and include substantially similar or
identical features as condyle portion 18. Additionally, while
described and depicted herein as having two condyle portions 16,
18, femoral component 10 may be formed as a unicondylar prosthesis
having only a single condyle portion. Referring to FIGS. 1 and 2,
articulating material 14 defines articulating surfaces 20 of
condyle portions 16, 18.
[0029] In one exemplary embodiment, base material 12 and
articulating material 14 are selected from different classes of
materials. For example, in one exemplary embodiment, base material
12 is a non-polymeric material, such as a biocompatible metal or
ceramic, and articulating material 14 is a polymer or hydrogel. For
example, if base material 12 is a ceramic, the ceramic may be an
oxide ceramic, such as alumina or zirconia; a non-oxide ceramic,
such as silicon nitride or silicon carbide; or other ceramic
materials that are biologically inert, and yet are sufficiently
hard and abrasion resistant. In addition, the ceramic may be a
monolith or, alternatively, the ceramic may be a plurality of
discrete microscopic or macroscopic particles held in a matrix.
Additionally, if base material 12 is a metal, the metal may be
titanium, a titanium alloy, cobalt chromium, cobalt chromium
molybdenum, stainless steel, porous tantalum, and/or a highly
porous biomaterial, for example.
[0030] A highly porous biomaterial is useful as a bone substitute
and/or a cell and tissue receptive material. A highly porous
biomaterial may have a porosity as low as 55, 65, or 75 percent and
as high as 80, 85, or 90 percent. An example of such a material is
produced using Trabecular Metal.TM. technology generally available
from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal.TM. is a
trademark of Zimmer Technology, Inc. Such a material may be formed
from a reticulated vitreous carbon foam substrate which is
infiltrated and coated with a biocompatible metal, such as
tantalum, etc., by a chemical vapor deposition ("CVD") process in
the manner disclosed in detail in U.S. Pat. No. 5,282,861, the
disclosure of which is expressly incorporated herein by reference.
In addition to tantalum, other metals such as niobium, or alloys of
tantalum and niobium with one another or with other metals may also
be used.
[0031] Generally, the porous tantalum structure includes a large
plurality of ligaments defining open spaces therebetween, with each
ligament generally including a carbon core covered by a thin film
of metal such as tantalum, for example. The open spaces between the
ligaments form a matrix of continuous channels having no dead ends,
such that growth of cancellous bone through the porous tantalum
structure is uninhibited. The porous tantalum may include up to
75%-85% or more void space therein. Thus, porous tantalum is a
lightweight, strong porous structure which is substantially uniform
and consistent in composition, and closely resembles the structure
of natural cancellous bone, thereby providing a matrix into which
cancellous bone may grow to provide fixation of base material 12 of
femoral component 10 to the bone stock of the distal femur.
[0032] The porous tantalum structure may be made in a variety of
densities in order to selectively tailor the structure for
particular applications. In particular, as discussed in the
above-incorporated U.S. Pat. No. 5,282,861, the porous tantalum may
be fabricated to virtually any desired porosity and pore size, and
can thus be matched with the surrounding natural bone in order to
provide an improved matrix for bone ingrowth and
mineralization.
[0033] As set forth above, in one exemplary embodiment,
articulating material 14 of femoral component 10 is a polymer. In
this embodiment, articulating material 14 may be polyethylene, a
poly ether ether ketone, fiber reinforced poly ether ether ketone,
ultrahigh molecular weight polyethylene, crosslinked ultrahigh
molecular weight polyethylene, polyether ketone ether ether ketone,
poly ether ketone ketone, polycarbonate urethane, polyphenylene,
and/or an antioxidant stabilized ultrahigh molecular weight
polyethylene, for example. In one exemplary embodiment,
articulating material 14 is formed from PrimoSpire.TM. self
reinforced polyphenylene, commercially available for SOLVAY
Advanced Polymers, LLC, of Alpharetta, Ga. PrimoSpire.TM. is a
trademark of SOLVAY Advanced Polymers, LLC, of Alpharetta, Ga.
Advantageously, by utilizing a rigid base material 12, such as a
metal, with a more resilient articulating material 14, such as a
polymer, wear of femoral component 10 may be reduced. In another
exemplary embodiment, as set forth above, articulating material 14
is a hydrogel. In this embodiment, articulating material 14 may be
polyvinyl pyrrolidinone, polyethylene ninyl alcohol, polystyrene
allyl alcohol, and/or bisphenos.
[0034] Additionally, in one exemplary embodiment, articulating
material 14 may be coated with a ceramic layer, which articulates
against a tibial component or natural tibia during normal knee
articulation. In exemplary embodiments, the ceramic layer on
articulating material 14 is formed by methods known by those
skilled in the art, such as, by plasma spray, flame spray, HVOF
spray, cold spray, or other spray coating technique that provides
bonding without substantial degradation of articulating material
14. In addition, the ceramic coating may also be formed on
articulating material 14 by ion implantation, ion beam assisted
deposition, CVD, or PVD, as is known in the art.
[0035] Referring to FIGS. 3 and 4, grooves 22, 24 are formed within
condyle portions 16, 18, respectively, of femoral component 10 for
the receipt of articulating material 14. In one exemplary
embodiment, grooves 22, 24 are machined into condyle portions 16,
18. In another exemplary embodiment, femoral component 10 is cast
and/or formed to include grooves 22, 24. Advantageously, by casting
and/or forming femoral component 10 to include grooves 22, 24, the
need to machine grooves 22, 24 into femoral component 10 prior to
the attachment of articulating material 14 is eliminated. In other
exemplary embodiments, grooves 22, 24 may be prepared using a water
jet, electrical discharge machining (EDM), and/or grit blasting.
Once grooves 22, 24 are properly prepared, articulating material 14
may be received within grooves 22, 24 by the use of an adhesive,
welding, thermal spraying, dynamic cold spraying, plasma spraying,
insert molding, compression molding, injection molding, laser
cladding, and/or press fitting, for example. Additionally,
lubricious polymeric materials, such as 2-methacryloyloxyethyl
phosphorylchlorine can be grafted into groove 22, 24.
[0036] As shown in FIGS. 3 and 4, groove 24 is at least partially
defined by wall 26. Wall 26 extends from bottom 28 of groove 24 to
upper surface 19 of condyle portion 18. As shown in FIG. 7,
articulating material 14 fills groove 24 (FIG. 3) and forms
articulating surface 20, which is substantially flush with upper
surface 19 of condyle portion 18. Advantageously, by positioning
articulating surface 20 substantially flush with upper surface 19,
smooth articulation of a tibial prosthesis and/or the natural
tibial with femoral component 20 is achieved. Specifically, in the
event that during normal knee articulation, a portion of the tibial
prosthesis or the natural tibia advances off of articulating
surface 20 and onto upper surface 19, this transition will occur
smoothly, as no sudden increase and/or decrease in the height of
the surface against which the tibial prosthesis or natural tibia is
articulating is encountered.
[0037] Referring to FIG. 9, in one exemplary embodiment, depth D of
groove 24 is less than or equal to 2 mm. This depth typically
provides a sufficient amount of articulating material 14 for
articulation against a corresponding tibial component of a knee
system or a natural tibia, while allowing base material 12 to
provide the additional strength and rigidity needed in condyle
portions 16, 18. In other exemplary embodiments, grooves 22, 24 may
have a depth D of greater than or less than 2 mm. For example, in
exemplary embodiments, grooves 22, 24, may have a depth D as small
as 0.5 mm, 1.0 mm, 1.5, mm, or 2.0 mm, and as large as 2.5 mm, 3.0
mm, 3.5 mm, or 4.0 mm. Additionally, while described and depicted
herein with specific reference to groove 24, groove 22 of condyle
portion 16 may be formed in a substantially similar manner as
groove 24.
[0038] Advantageously, the design of grooves 22, 24 and the
surrounding of articulating material 14 received within grooves 22,
24 by base material 12 substantially prevents the delamination of
articulating material 14 from base material 12. Base material 12 of
femoral component 10 may be characterized as occupying a volume
that is substantially greater than the volume of articulating
material 14. Thus, base material 12 and, correspondingly, femoral
component 10 may not substantially deflect while under load. The
rigidity of base material 12 may permit uniform, predictable, and
consistent loading of articulating surface 20. Consequently, when
loaded, articulating surface 20 receives substantially uniform
frictional contact with an opposing articular surface on the
natural tibia or tibial prosthesis, and thus, rigidity of base
material 12 may limit abrasion along any specific portion of
articulating surface 20. Moreover, articulating material 14 of
femoral component 10 may exhibit some elasticity during loading to
allow axial deflection or deformation of articulating material 14.
Therefore, pressures exerted on femoral component 10 may be
partially absorbed during elastic motion of articulating material
14. Further, the additional rigidity provided by base material 12
helps to prevent articulating material 14 from shearing or
otherwise separating from base material 12.
[0039] In another exemplary embodiment, shown in FIGS. 8 and 9,
condyle portion 18 further includes lip 30. Lip 30 extends from
wall 26 and cooperates with wall 26 to define groove 24. In one
exemplary embodiment, shown in FIG. 9, lip 30 extends inwardly from
wall 26 in the direction of groove 24 as lip 30 approaches
articulating surface 20 and upper surface 19 of condyle portion 18
and forms an obtuse angle .alpha. with wall 26. As shown in FIG. 9,
angle .alpha. extends between wall 26 and lip 30. In exemplary
embodiments, angle .alpha. is as small as 95 degrees, 120 degrees,
130 degrees, and 145 degrees and as large as 150 degrees, 160
degrees, and 170 degrees.
[0040] Further, due to lip 30 extending inwardly from wall 26 in
the direction of groove 24, lip 30 facilitates the retention of
articulating material 14 within groove 24, as the interaction of
lip 30 with articulating material 14 substantially prevents removal
and/or delamination of articulating material 14 from groove 24.
Specifically, as articulating material 14 advances in the direction
of lip 30, articulating material 14 contacts lip 30. In order for a
portion of articulating material 14 to be positioned outside of
groove 24, at least a portion of articulating material 14 has to be
deformed in order to pass by lip 30. However, due to lip 30
extending at least partially over the perimeter of articulating
material 14 and the material properties of articulating material
14, articulating material 14 is not deformed during normal knee
articulation to the extent necessary to cause articulating material
14 to deform inwardly and allow articulating material 14 to pass by
lip 30. Therefore, removal and/or delamination of articulating
material 14 from groove 24 is substantially prevented. In addition,
attachment of articulating material 14 is improved by base material
12 fully supporting articulating material 14 within groove 24.
[0041] Referring to FIG. 5, a tibial prosthesis is shown in the
form of tibial component 40. Tibial component 40 is a monoblock
tibial prosthesis, i.e., is formed entirely from a single material,
and is configured for independent attachment to the tibia, i.e., is
attached to the tibia without the need for using an additional
tibial component to support and/or retain tibial component 40 in
position. For example, in a traditional tibial prosthesis, the
articulating component is supported by and/or secured to a tray
component. By using tibial component 40, the need for a tray
component is eliminated and tibial component 40 may be secured
directly to a tibia in a known manner, such as by a press-fit or
with bone cement, for example.
[0042] Tibial component 40 includes attachment surface 42 and
articulating surfaces 44, 45. Attachment surface 42 is configured
for attachment to the bone stock of the proximal end of a tibia.
Similarly, articulating surfaces 44, 45 are configured for
articulation with articulating surfaces 20 of articulating material
14 of femoral component 10 and/or the condyles of a natural femur.
While described and depicted herein as including two articulating
surfaces 44, 45 that articulate with opposing natural or prosthetic
femoral condyles, tibial component 40 may be formed as a
unicondylar prosthesis having only a single articulating surface.
In one exemplary embodiment, tibial component 40 is formed from a
polymer, such as poly ether ether ketone, fiber reinforced poly
ether ether ketone, ultrahigh molecular weight polyethylene,
cross-linked ultrahigh molecular weight polyethylene, and polyether
ketone ether ether ketone. Alternatively, tibial component 40 may
be formed from a hydrogel, such as polyvinyl pyrrolidinone,
polyethylene ninyl alcohol, polystyrene allyl alcohol, and
bisphenos. In another exemplary embodiment, tibial component 40 is
formed from a metal, such as titanium, titanium alloy, cobalt
chromium, cobalt chromium molybdenum, porous tantalum, and/or a
highly porous biomaterial, for example. Alternatively, in another
exemplary embodiment, tibial component 40 is formed from another
class of materials, such as ceramics. For example, tibial component
40 may be formed from an oxide ceramic, such as alumina or
zirconia; non-oxide ceramic, such as silicon nitride or silicon
carbide; or other ceramic materials that are biologically inert,
and yet are sufficiently hard and abrasion resistant. In addition,
tibial component 40 may be a monolith or, alternatively, may be
formed form a plurality of discrete microscopic or macroscopic
particles held in a matrix.
[0043] Referring to FIGS. 6 and 11, tibial component 50 is shown
including body 51 and articulating portions 47, 49 defining
articulating surfaces 54, 55. Body 51 defines upper surface 61
attachment surface 52 for securement of tibial component 50 to a
tibial tray and/or directly to a resected, proximal tibia. As shown
in FIG. 11 with respect to articulating portion 47, articulating
portions 47, 49 of tibial component 50 are formed independently of
body 51 of tibial component 50. Specifically, articulating portions
47, 49 may be formed from a non-polymeric material, such as a
biocompatible metal and/or ceramic. For example, if articulating
portions 47, 49 are formed from a metal, articulating portions 47,
49 may be formed from titanium, a titanium alloy, cobalt chromium,
zirconium alloys, tantalum, and/or cobalt chromium molybdenum.
Additionally, if articulating portions 47, 49 are formed from a
ceramic, articulating portions 47, 49 may be formed from oxide
ceramic, such as alumina or zirconia; non-oxide ceramic, such as
silicon nitride or silicon carbide; or other ceramic materials that
are biologically inert, and yet are sufficiently hard and abrasion
resistant.
[0044] In contrast to articulating portions 47, 49, body 51 is
formed from a different class of materials, such as polymers, a
highly porous biomaterial, or a hydrogel. For example, body 51 may
be formed from polyethylene, a poly ether ether ketone, fiber
reinforced poly ether ether ketone, ultrahigh molecular weight
polyethylene, crosslinked ultrahigh molecular weight polyethylene,
polyether ketone ether ether ketone, poly ether ketone ketone,
polycarbonate urethane, polyphenylene, PrimoSpire.TM. self
reinforced polyphenylene commercially available from SOLVAY
Advanced Polymers, LLC, of Alpharetta, Ga., and/or an antioxidant
stabilized ultrahigh molecular weight polyethylene, for example.
Additionally, body 51 may be formed from polyvinyl pyrrolidinone,
polyethylene ninyl alcohol, polystyrene allyl alcohol, and
bisphenos.
[0045] Advantageously, by utilizing tibial component 50, body 51,
formed, for example, from a polymer, acts to provide cushioning
and/or to dampen the shock transmitted to the knee prosthesis
during normal joint articulation. Specifically, body 51 of tibial
component 50 may exhibit some elasticity during loading to allow
axial deflection and/or deformation of the body 51 between the
proximal tibia and articulating portions 47, 49. Thus, pressures
exerted on tibial component 50 may be partially absorbed and
dispersed by body 51 with little or no wear of articulating
portions 47, 49. Additionally, in order to reduce friction, the
metallic and/or ceramic portions of tibial components 40, 50 may be
treated by nitriding or coated with titanium nitride, chromium
nitride, molybdenum disulfide, or zirconium nitride. Further, when
body 51 is formed from a highly porous biomaterial, a good implant
fixation may be achieved.
[0046] In order to connect articulating portions 47, 49 to body 51
of tibial component 50, articulating portions 47, 49 may be
press-fit into body 51. Alternatively, articulating portions 47, 49
may include a peg or plurality of pegs extending therefrom onto
which body 51 may be molded, such as by injection or compression
molding, or otherwise formed. Articulating portions 47, 49 may also
be secured to body 51 of tibial component 50 with an adhesive, by
welding, or by sol gel processing. Regardless of the method used to
secure articulating portions 47, 49 to body 51, articulating
portions 47, 49 are positioned such that articulating surfaces 54,
55 are flush with upper surface 61 of body 51, as shown in FIG. 11
with respect to articulating surface 54. In this manner, the
perimeters of articulating portions 47, 49 are surrounded and
supported by body 51. Advantageously, attachment of articulating
portions 47, 49 to body 51 is improved by body 51 fully supporting
and surrounding articulating portion 47, 49. Further, by
positioning articulating surfaces 54, 55 of articulating portions
47, 49 substantially flush with upper surface 61 of body 51, smooth
articulation of a femoral prosthesis and/or the natural femur with
tibial component 50 is achieved. Specifically, in the event that
during normal knee articulation, a portion of the femoral
prosthesis or natural femur advances off of either of articulating
surfaces 54, 55 and onto upper surface 61, this transition will
occur smoothly, as no sudden increase and/or decrease in the height
of the surface against which the femoral prosthesis or natural
femur is articulating is encountered.
[0047] Further, as shown in FIG. 6, articulating surfaces 54, 55 of
articulating portions 54, 55 may also include a plurality of
dimples 56, such as those disclosed in U.S. patent application Ser.
No. 11/684,028, the entire disclosure of which is expressly
incorporated by reference herein. Dimples 56 facilitate the
retention of synovial fluid and/or other fluids on tibial component
50 to provide lubrication to articulating surfaces 54, 55. To form
dimples 56, dimpling, laser ablation, and/or honing may be
utilized. Additionally, in one exemplary embodiment, dimples 56
have an RSa roughness of less than 10 micrometers. By having a RSa
roughness of less than 10 micrometers, any interference of dimples
56 with the articulation of femoral component 10 and tibial
component 50 is substantially eliminated. In order to achieve a RSa
roughness of less than 10 micrometers, chemical or electrolytic
polishing may be utilized. Additionally, while described and
depicted herein with specific reference to articulating surfaces
54, 55 of tibial component 50, dimples 56 may also be applied to
articulating surfaces 44, 45 of tibial component 40 and/or
articulating surfaces 20 of femoral component 10.
[0048] In one exemplary embodiment, shown in FIGS. 12 and 13, body
51 and, specifically, attachment surface 52 of tibial component 50
are configured to mate with a corresponding tibial tray component
100. Tibial tray component 100 includes plate 102, keel 104, and
stem 106. Stem 106 and keel 104 are configured for receipt within
the intramedullary canal of the tibia. Keel 104 acts to provide
stabilization to tray component 100 and prevent rotation of tray
component 100 once tray component 100 has been implanted in the
tibia. Plate 102 includes lower surface 108 configured to seat
against a resected portion of the proximal tibia. Support surface
110 of plate 102 is configured to receive and support body 51 of
tibial component 50 thereon. In one exemplary embodiment, body 51
is secured to plate 102 by forming a snap-fit or an interference
fit with plate 102. In one exemplary embodiment, plate 102 includes
rim portions 112 extending upwardly from support surface 110. Body
51 of tibial component 50 may be includes recesses that engage rim
portions 112 to form a snap-fit or, alternatively, body 51 may be
sized such that perimeter surfaces of body 51 form an interference
fit with rim portions 112.
[0049] In one exemplary embodiment, tray component 100 is formed
from a metal. For example, tray component 100 may be formed from
titanium, a titanium alloy, cobalt chromium, cobalt chromium
molybdenum, stainless steel, porous tantalum, and/or a highly
porous biomaterial. Thus, referring to FIG. 13, three different
materials may be used to form a tibial prosthesis that supports a
femoral component or the natural femur atop a resected proximal
tibia during knee articulation. Specifically, a first material may
be used to form articulating portions 47, 49 of tibial component
50, a second material may be used to form body 51 of tibial
component 50, and a third material may be used to form plate 102 of
tray component 100. For example, in one exemplary embodiment,
articulating portions 47, 49 may be formed from a ceramic, body 51
of tibial component 50 may be formed from a polymer, and tray
component 100 may be formed from a metal. Alternatively, in another
exemplary embodiment, articulating portions 47, 49 of tibial
component 50 are formed from a first metal, body 51 of tibial
component 50 is formed from a polymer, and plate 102 of tray
component 100 is formed from a second metal, which is different
than the first metal. By adjusting the stiffness of the various
components of tibial component 50 and/or tray component 100, a
natural knee feel may be achieved.
[0050] Another exemplary embodiment of tibial component 40 is shown
in FIG. 10 as tibial component 60. Tibial component 60 is
substantially similar to tibial component 40 and corresponding
reference numerals have been used to identify identical or
substantially identical features therebetween. Tibial component 60
further includes chamber 46 formed therein. Specifically, chamber
46 is formed within tibial component 60 between attachment surface
42 and articulating surface 44. Chamber 46 may have a length of up
to substantially 10 mm and a height of up to substantially 3 mm. As
a result of forming tibial component 60 as a monoblock or monolith,
sufficient rigidity and strength is provided by tibial component 60
even after chamber 46 is formed therein. Passageways 48, which in
one exemplary embodiment are microsized, extend from chamber 46 to
articulating surface 44 of tibial component 60. In this embodiment,
fluid, such as an antibiotic, medicinal, synovial, and/or other
fluids, may be received within chamber 46. Then, during natural
articulation of tibial component 60 with femoral component 10, the
fluid contained within chamber 46 may travel through passageways 48
and exit to articulating surfaced 44. Thus, by utilizing chamber 46
and passageways 48 in conjunction with tibial component 60, a
mechanism for providing continual lubrication or medicinal
treatment to the knee joint is provided.
[0051] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *